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Finding Neptune from Jupiter (Finder Chart), April to September 2009 |
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Star map showing the path of Neptune against the backdrop of stars in Capricornus and Aquarius from August 2006 to September 2023. Positions are marked for each opposition date. Neptune begins the period describing a series of shallow 'hybrid' formations (part zig-zag, part loop) having crossed the ecliptic from North to South in 2003. By the time the planet is South of the Circlet of Pisces, the 'hybrid' loops have transformed into conventional, South-facing loops (the individual 'loops' are not discernible in this chart because of the scale of the map; instead, each loop appears as an oblique line). Note that, because the angular width of Neptune's loops (about 2º.8 across) are greater than its annual orbital motion, each successive loop overlaps (in longitude) with the next. The star map applies to observers in the Northern hemisphere (i.e. North is up); for the Southern hemisphere view, click here. Printer-friendly versions of this chart are available for Northern and Southern hemisphere views (the above chart will help in finding the general location of the planet throughout the period in question, however a more detailed star chart will be required to pinpoint the planet precisely - for more details, see below). |
The Position of Neptune in the Night Sky, 2006 to 2023 by Martin J Powell
From August 2006 to March 2010, Neptune continues its motion through Capricornus, the Sea-Goat, where it has been situated since early 1998. From March 2010, Neptune enters the constellation of Aquarius, the Water Carrier. The planet enters Pisces, the Fishes, in April 2022 where it will remain until 2039.
Neptune reaches opposition to the Sun (when it is closest to the Earth and brightest in the sky for the year) every 367½ days on average, i.e. about 2½ days later in each successive year. The apparent magnitude of the planet varies little during the period shown in the star chart - from +7.8 (at opposition) to +8.0 (at superior conjunction).
The apparent diameter of the planet (its angular size when seen from the Earth) at opposition throughout the period covered by the star chart is 2".4 (2.4 arcseconds, where 1 arcsecond = 1/3600th of a degree).
In 2010, Neptune will complete its first orbit since it was discovered on September 23rd, 1846. The planet is at its 1846 position in the sky (i.e. at the same longitude measured relative to the Earth) in mid-April 2009 (moving direct), in mid-July 2009 (moving retrograde) and again in early February 2010 (moving direct). Neptune will return to its discovery position in its orbit (i.e. at the same longitude measured relative to the Sun) in late June 2010.
Neptune will cross the celestial equator in Pisces in April 2026 (heading North-eastwards and moving direct), in August 2026 (moving retrograde and temporarily heading South-westwards) and again in January 2027 (resuming North-easterly motion, moving direct). For the first time in over 81 years, the planet will then become visible for a longer period of time in the Northern hemisphere than in the Southern hemisphere (it last crossed the celestial equator - as it headed Southwards along the ecliptic - in Virgo in 1944).
Looking further ahead, the planet will continue its Northward motion along the ecliptic until it reaches its most Northerly point in Gemini in 2067, having crossed its perihelion point (i.e. its closest point to the Sun; in this case 29.81 Astronomical Units or 4.46 thousand million kms) in Aries in 2046.
[Terms in yellow italics are explained in greater detail in an associated article describing planetary movements in the night sky.]
Twins Reunited
Further to the North-east (from March 2009, moving through Pisces) is Neptune's planetary neighbour and 'twin'- Uranus. Seen from the viewpoint of the Earth, faster-moving Uranus 'overtook' Neptune when the two planets were in Sagittarius in July 1993 (at which point they were in conjunction, i.e. at the same celestial longitude). This was the first time the two planets had been seen at conjunction since they were discovered (Uranus in 1781, Neptune in 1846). Conjunctions of these two planets are rare events, taking place about every 172 years; the next one will be in the year 2164.
Finding Neptune in Your Local Night Sky (General Location)
Where in the night sky should I look for Neptune tonight? In which direction and how high up will it be?
The location of a planet (or any other celestial body) in your local night sky depends upon several factors: the constellation in which it is positioned, your geographical latitude and longitude, the local season and the date and time at which you observe. To find a planet in the night sky at any particular date and time, we must know two things: a direction in which to look along the observer's horizon (eg. Southeast, East-Southeast) and an angle to look above the horizon (known as altitude or elevation).
Use the following Javascript program to help find Neptune in your night sky during the year:
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For additional information on the fully-functional version of the program, see here. |
Mini-AstroViewer® is an easy-to-use Java applet which shows the positions of the celestial bodies in the night sky for any location on the globe at any time of the year (Javascript must be enabled in your browser for the program to function). To activate the program, click on the button below (the program will open in a pop-up window). The default location is New York, USA. To select your own location and then find the planets, refer to the 'Finding Neptune ..' box below. An animated tutorial showing how to locate a planet in the night sky using Mini-AstroViewer® can be seen here.
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Finding Neptune in Your Own Night Sky using Mini-AstroViewer®
To set your own location, click on the 'Location' button and click on your approximate position on the pop-up world map. If you know your precise latitude and longitude, you can refine your position by pressing the left/right and up/down arrows to move the cross-hair in 1° increments (to find your latitude and longitude, visit the Heavens Above website, select your country and enter the name of your nearest town or city using the 'Town Search' facility). Having plotted your geographical co-ordinates, click 'OK' and the night sky over your own location will appear in the window, valid for the current time, which is displayed in UT (Universal Time, equivalent to GMT). The applet will initialise displaying the current UT time according to your browser's clock and Time Zone settings (if you would prefer to have the Local Time displayed, use the fully-functional version of the program at Astroviewer.com). The red circle represents the horizon around you; the lower half of the display represents the part of the sky you are facing. The centre of the circle is the point directly above your head (known as the zenith). The ecliptic (the path along which the Sun, Moon and planets will be found) is marked by a red dashed line, passing as it does through the zodiac constellations. The blue dashed line marks the apparent position of the celestial equator, which arcs across the sky from the due East point on the horizon to the due West point. The program plots stars down to magnitude +5.0. The bottom scroll bar rotates the horizon view, allowing for a view in any compass direction; the left-hand scroll bar zooms the sky in or out, and the right-hand scroll bar pans up (to the zenith) or down (to the horizon) whenever the view has been zoomed.
Infomation on a celestial body can be viewed by clicking on the object (in the case of a planet, its magnitude, distance, elongation and apparent diameter). Note that if Neptune's elongation (its angular distance from the Sun as seen from the Earth) is less than about 20°, it will not be visible because it is too near the Sun. Remember that local twilight can affect the visibility of a particular planet, even at elongations greater than 20°, making observation difficult or even impossible. This particularly applies throughout the local summer months at higher latitudes. To find the general location of Neptune in your Night Sky, first see if it is above the horizon at the time you are requesting. If it is visible within the circle, move the bottom scroll bar left or or right to rotate the image until the planet is positioned on the vertical red line (the altitude scale). Zoom in to the area using the left-hand scroll bar where necessary (see animation opposite). The direction of Neptune at the requested time will be indicated at the bottom (W, SW, etc). The altitude of the planet (its angle above the horizon) can be read off on the altitude scale (it is marked at 10° intervals). Hence if it is three notches up, its altitude is 30° at the displayed time (to understand how to determine a planet's altitude in the night sky, refer to the explanatory diagrams below). If Neptune's altitude is less than about 10° it will probably be difficult or impossible to see because of the dimming effect of the Earth's atmosphere and, in town and city locations, the effects of light pollution or skyglow. If
Neptune is not shown within the circle, it is below the horizon
and you will have to wait until after it next rises before you can see
it (provided it is not too near the Sun). To find when it next rises,
click the 'hours forward' button ( If Neptune rises in daylight (i.e. if the Sun is already above the horizon), you will have to wait until after dusk to see it - in which case, 'fast forward' to a time shortly after sunset, then note down the time and direction. This will provide you with the general location of the planet in your Night Sky at the time you have requested. A more detailed 'star hop' will be required to pinpoint the planet precisely - for details, see the 'Finding Neptune' sections below.
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Finding Neptune from Jupiter, April to September 2009
During 2009 the bright planet Jupiter passes Neptune near the Capricornus/Aquarius border, describing its significantly larger planetary 'loop' about one apparent Full Moon-diameter to the South of Neptune. Since Jupiter is such an easy naked-eye object (use the Mini-AstroViewer® Java applet above to find it), the close approach of the two planets in 2009 provides a good opportunity to find Neptune with relative ease; for this purpose, a finder chart is provided below.
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| Paths of Jupiter and Neptune, in North-eastern Capricornus, shown at 10-day intervals for the period April 4th to September 11th 2009. Much of the star field in the chart should be easily contained within a binocular field of view (which typically ranges from 5° to 9°). Stars are shown down to magnitude +8.5. Right Ascension and Declination co-ordinates are marked around the border, for cross-referencing in a star atlas. A Southern hemisphere view can be found here. Printer-friendly (greyscale) versions of the chart are available for Northern and Southern hemisphere views. Move your pointer over the chart (or click here) to see a 'clean' star map of the area (without planet paths); observers may wish to use the 'clean' star map as an aid to plotting the two planets' positions on a specific night - in which case, a printable version can be found here. Two of the three conjunctions between these planets (see below) take place during the period indicated on the chart, i.e. on May 25th and July 13th (at which times, a line drawn vertically through the two planets show them to be in alignment). After September 11th (when Jupiter exits the chart area) the position of Neptune is continued - marked by individual points - through to October 21st 2009 for those who wish to continue looking for the planet up to that time. Having identified Neptune's location, the author recommends that Jupiter be positioned just outside the binocular field to minimise the likely effects of glare from that planet. Ideally, searches for Neptune should be carried out on Moonless nights, i.e. in the two-week period centred on the New Moon in any given month. The apparent magnitudes of selected stars in the region (down to magnitude +8.5) are shown in brackets in this chart. |
The Jupiter-Neptune Triple Conjunction, May to December 2009
As Jupiter and Neptune pass each other in the sky during 2009, they undergo a series of three conjunctions (i.e. they reach the same celestial longitudes) over a seven-month period; this is referred to as a triple conjunction, and they are relatively rare events (the last one between Jupiter and Neptune took place in 1971).
The first of the 2009 conjunctions took place on May 25th 2009, when Jupiter (at magnitude -2.4) was moving direct (or prograde, i.e. West to East) against the star background and Neptune (at magnitude +7.9) was approaching its Eastern stationary point. The two planets were separated vertically by 25' (25 arcminutes, or just under half a degree) at this point, and were visible in the morning sky before sunrise. The second conjunction takes place on July 13th 2009, when both Jupiter (mag. -2.7) and Neptune (mag. +7.8) are retrograding (moving East to West) against the star background; the planets are separated by 36' (0°.6) at this point, and are visible from the late evening onwards. Jupiter then reaches opposition to the Sun on August 14th (having brightened to mag. -2.8), followed only three days later by Neptune (at mag. +7.8). Finally, the planets are again in conjunction on December 20th 2009, when both Jupiter (-2.2) and Neptune (+7.9) have resumed direct motion, the pair then being separated by 33' (0°.55); this conjunction is visible in the evening sky, shortly after sunset.
The next triple conjunction between these two planets will be in 2047-8, when they are both in Aries. Conjunctions of any kind between these two planets (mostly single or double) occur, on average, about every 12.6 years. The next will be on April 12th 2022 (single, on the Aquarius/Pisces border) then on March 25th 2035 (single, in Pisces); both of these conjunctions will be difficult to see because the two planets will be close to the Sun at the time.
A point should be made regarding the planetary conjunction dates mentioned here. There are in fact two ways of defining a conjunction date: one is measured in Right Ascension (i.e. along the celestial equator) and the other is measured along the ecliptic, which is inclined at 23½° to the Earth's equatorial plane (this is due to the tilt of the Earth's axis in space). Conjunction dates measured in Right Ascension (RA) apply whenever two planets (or any two celestial bodies) attain the same Right Ascension; those measured along the ecliptic apply whenever two celestial bodies attain the same ecliptic longitude (which is measured in degrees Eastwards from the First Point of Aries). The conjunction dates determined by each method can differ by up to several days, particularly when conjunctions occur in the vicinity of Pisces and Virgo, i.e. the constellations in which the ecliptic intersects with the celestial equator. Although dates determined using the ecliptic longitude method are technically more accurate (separations between planets can be significantly closer) the Right Ascension method is the more commonly used, and it is the one which is adopted here.
An animation demonstrating the principle of the triple conjunction - and showing how conjunction dates are determined - can be found on the Uranus 2006-2019 page.
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The Current Night Sky over
Hong
Kong
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Would you like to see your own town or city shown here?
Requested locations may appear on another planet page (see links below) depending upon the number of requests received by the author at any given time. A list of the night sky locations currently displayed on this website can be seen on the main Naked-eye planets page. The graphic shows the sky at the location indicated when this page was loaded in your browser; if several minutes have since passed, click the 'Refresh' button at the top of your browser (or press the F5 key) to see the current sky. The Night Sky location displayed here is periodically changed by the website author. Additional AstroViewer® Information Mini-AstroViewer® is a lightweight version of AstroViewer®, an interactive night sky map that helps you find your way in the night sky quickly and easily. Due to its intuitive interface, it is well suited to beginners in astronomy. The fully functional, free-to-use version can be accessed at the AstroViewer® website. It has additional features such as a Local Time display, a planet visibility chart for any selected location, a 3D Solar System map, the ability to store user-generated world locations, a 'Find Celestial Body' facility, printing and language options and greater flexibility in the night sky display (see details here). A fully-functional version for offline use can be obtained upon the purchase of a license key, following the download and installation of a test version. AstroViewer® is produced by Dirk Matussek. |
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Atlas of Neptune Garry E. Hunt & Sir Patrick Moore |
Neptune: The Planet, Rings & Satellites Ellis D. Miner & Randii R. Wessen |
Uranus, Neptune and Pluto and How to Observe Them (Astronomers' Observing Guides) Richard Schmude, Jr |
Capturing The Stars Astrophotography by the Masters Robert Gendler & Neil deGrasse Tyson |
Make Time for The Stars: Fitting Astronomy Into Your Busy Life Antony Cooke |
The Rainbow Sky An Exploration of Colors in the Solar System and Beyond Tony Buick |
Star Maps: History, Artistry and Cartography (Springer-Praxis Books in Popular Astronomy) Nick Kanas |
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Finding Neptune from 2009 to 2023
Through to March 2010, pale-blue Neptune is located in the Eastern half of Capricornus. To find Capricornus, first locate the asterism (star pattern) unofficially known as 'The Steering Wheel', near the Northern border of Aquarius ('The Steering Wheel' is found by looking West of the Circlet of Pisces, which itself is found by looking South of the Great Square of Pegasus! For a star map of this region, see the Uranus 2006-2019 page). Use the Mini-AstroViewer® Java applet above to help locate these constellations in your local night sky.
The 'Steering
Wheel' asterism, together
with its nearby star Sadalmelik (also known as 
Aqr or Alpha Aquarii, apparent
magnitude +2.9) is the most recognisable
feature of Aquarius.
A 'star-hop'
will be required from 'The Steering
Wheel' and
Sadalmelik to the star Sadalsuud (
Aqr or Beta Aquarii, also magnitude +2.9)
and then Southwards to the star Deneb Algiedi (
Cap or Delta Capricorni,
magnitude +2.9) in the tail of Capricornus.
Note that the stars Sadalmelik, Sadalsuud and Deneb Algiedi
form an inverted triangle, which should help with the star-hopping procedure. When
at Deneb Algiedi, you are within only a few degrees of Neptune,
after which a larger-scale finder chart will be needed to pinpoint the
planet precisely using binoculars (of which, see below). Also marked on the
star map are the stars 
Cap (Nashira or Gamma Capricorni, mag. +3.6) and 
Cap
(Iota Capricorni, mag. +4.2), both of which should help in pinpointing the
planet when using finder charts.
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Neptune, the most difficult of the 'true planets' to find, photographed here in moderately light-polluted conditions in August 2005, when the planet was in central Capricornus. The planet, barely perceptible in the main picture, appears in the upper left of the rectangular enlargement (move your pointer over the image to reveal the star magnitudes, or click here). When mounted on a tripod, modern-day digital cameras fitted with a zoom lens will detect the planet at shutter speeds of only a couple of seconds at higher ISO (film speed) settings. Some photos will even show the planet's characteristic blue-grey colouration. The field of view of the main picture is approximately 2º.3 by 1º.9; that of the inset rectangle is about 0º.43 by 0º.03 (i.e. 25.8 by 18.4 arcminutes). |
From
March 2010, Neptune
enters Aquarius,
wherein the planet can be found by star-hopping Southwards from 'The Steering
Wheel' asterism
towards Sadalmelik and then Ancha (
Aqr or Theta Aquarii, magnitude +4.1).
From April 2022, Neptune enters Pisces, whose most recognisable feature is the asterism known as the Circlet of Pisces. The planet will be situated to the South of the Circlet, whereby a star-hop will be required, with the assistance of a finder-chart.
Around all opposition dates shown on the star map, Neptune will be due South at local midnight in the Northern hemisphere (due North at local midnight in the Southern hemisphere).
Finding Finder Charts for Neptune on the Web
Finder charts for locating Neptune - showing a smaller area of sky and fainter stars - are published on a variety of websites, such as Paul Money's AstroSpace site and the Royal Astronomical Society of New Zealand (in this case the available star chart shows the Southern hemisphere view, with South up and East to the right; they will need to be inverted for the Northern hemisphere view). Northern hemisphere charts for the current year can usually be found at the Sky & Telescope website by performing a search there on finding Neptune and clicking on the appropriate result. Charts at other websites can be found by using the following search engines (be sure to check the correct orientation of any chart found; it will need to be orientated North-up for Northern hemisphere observers and South-up for Southern hemisphere observers):-
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Northern Hemisphere |
Southern Hemisphere |
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Positions of the Superior Planets:
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Mars, 2009-2010 |
Jupiter, 2009-2011 |
Saturn, 2006-2013 |
Uranus, 2006-2018 |
Pluto, 2006-2022 |
Current Position of the Sun and the Brighter Naked-Eye Planets (Star Map)
Credits
Copyright © Martin J. Powell December 2006; updated February-June 2009
) repeatedly until the planet
appears over the eastern horizon, then note down the time and direction
this occurs. By clicking the 'minutes/hours forward' buttons (
